Steam generators can be used, for example, in a Rankine cycle or in a Clausius-Rankine cycle to be able to evaporate the working medium of the respective cycle. Such a steam generator may basically be equipped with a heat exchanger or be set up like a heat exchanger.
A waste heat recovery device that operates on the basis of a Rankine cycle or a Clausius-Rankine cycle usually comprises a waste heat recovery circuit, in which a suitable working medium circulates. In the waste heat recovery circuit, usually a steam generator for evaporating the working medium, an expansion engine for releasing the working medium, a condenser for condensing the working medium as well as a delivery means for driving the working medium in the waste recovery circuit are arranged in the flow direction of the working medium one behind the other. By means of such a waste heat recovery device, waste heat occurring, for example, in an internal combustion engine can be utilized to improve the energy efficiency of the internal combustion engine. For example, mechanical energy can be produced by means of the expansion engine, which can be used for supporting the internal combustion engine. It is likewise possible to produce current by means of the expansion engine in conjunction with a generator, which, especially in conjunction with a suitable energy storage means, can be utilized for supplying electrical components of the internal combustion engine or of a vehicle equipped with the internal combustion engine. So that such a waste heat recovery device has an especially high energy efficiency, the transmission of heat between a heating fluid, whose heat shall be utilized as waste heat, and the working medium of the waste heat recovery circuit is of great importance.
A heat exchanger means for a waste system of an internal combustion engine in a motor vehicle has become known from DE 10 2005 039 794 A1, whereby this waste gas heat exchanger has a heat exchanger channel, in which a heat exchanger is arranged. The heat exchanger means also has a bypass channel for bypassing the heat exchanger channel. For reducing the production costs of the heat exchanger means, the two channels are arranged, such that the one channel envelops the other channel. In the prior-art heat exchanger means, the heat exchanger is fluidically bound in a cooling circuit of the internal combustion engine, so that the internal combustion engine can be heated up rapidly via the waste gas, for example, in case of a cold start of the internal combustion engine. Enough heat is likewise available in the waste gas to heat a passenger compartment of a motor vehicle equipped with the internal combustion engine in the usual manner via the cooling circuit of the internal combustion engine.